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TAV: improved compression using some coefficient preprocessing

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This commit is contained in:
minjaesong
2025-09-29 01:17:53 +09:00
parent 01278815c7
commit 66909537a0
5 changed files with 280 additions and 47 deletions
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64
video_encoder/decoder_tav.c
View File

@@ -26,6 +26,27 @@ static inline int CLAMP(int x, int min, int max) {
return x < min ? min : (x > max ? max : x);
}
// Decoder: reconstruct coefficients from significance map
static void postprocess_coefficients(uint8_t *compressed_data, int coeff_count, int16_t *output_coeffs) {
int map_bytes = (coeff_count + 7) / 8;
uint8_t *sig_map = compressed_data;
int16_t *values = (int16_t *)(compressed_data + map_bytes);
// Clear output
memset(output_coeffs, 0, coeff_count * sizeof(int16_t));
// Reconstruct coefficients
int value_idx = 0;
for (int i = 0; i < coeff_count; i++) {
int byte_idx = i / 8;
int bit_idx = i % 8;
if (sig_map[byte_idx] & (1 << bit_idx)) {
output_coeffs[i] = values[value_idx++];
}
}
}
// TAV header structure (32 bytes)
typedef struct {
uint8_t magic[8];
@@ -558,27 +579,46 @@ static int decode_frame(tav_decoder_t *decoder) {
// Copy from reference frame
memcpy(decoder->current_frame_rgb, decoder->reference_frame_rgb, decoder->frame_size * 3);
} else {
// Read coefficients in TSVM order: all Y, then all Co, then all Cg
// Read coefficients with significance map postprocessing
int coeff_count = decoder->frame_size;
uint8_t *coeff_ptr = ptr;
// Read coefficients into temporary arrays
// Allocate arrays for decompressed coefficients
int16_t *quantized_y = malloc(coeff_count * sizeof(int16_t));
int16_t *quantized_co = malloc(coeff_count * sizeof(int16_t));
int16_t *quantized_cg = malloc(coeff_count * sizeof(int16_t));
for (int i = 0; i < coeff_count; i++) {
quantized_y[i] = (int16_t)((coeff_ptr[1] << 8) | coeff_ptr[0]);
coeff_ptr += 2;
// Postprocess coefficients from significance map format
// First find where each channel's data starts by reading the preprocessing output
size_t y_map_bytes = (coeff_count + 7) / 8;
// Count non-zeros in Y significance map to find Y data size
int y_nonzeros = 0;
for (int i = 0; i < y_map_bytes; i++) {
uint8_t byte = coeff_ptr[i];
for (int bit = 0; bit < 8 && i*8+bit < coeff_count; bit++) {
if (byte & (1 << bit)) y_nonzeros++;
}
}
for (int i = 0; i < coeff_count; i++) {
quantized_co[i] = (int16_t)((coeff_ptr[1] << 8) | coeff_ptr[0]);
coeff_ptr += 2;
}
for (int i = 0; i < coeff_count; i++) {
quantized_cg[i] = (int16_t)((coeff_ptr[1] << 8) | coeff_ptr[0]);
coeff_ptr += 2;
size_t y_data_size = y_map_bytes + y_nonzeros * sizeof(int16_t);
// Count non-zeros in Co significance map
uint8_t *co_ptr = coeff_ptr + y_data_size;
int co_nonzeros = 0;
for (int i = 0; i < y_map_bytes; i++) {
uint8_t byte = co_ptr[i];
for (int bit = 0; bit < 8 && i*8+bit < coeff_count; bit++) {
if (byte & (1 << bit)) co_nonzeros++;
}
}
size_t co_data_size = y_map_bytes + co_nonzeros * sizeof(int16_t);
uint8_t *cg_ptr = co_ptr + co_data_size;
// Decompress each channel
postprocess_coefficients(coeff_ptr, coeff_count, quantized_y);
postprocess_coefficients(co_ptr, coeff_count, quantized_co);
postprocess_coefficients(cg_ptr, coeff_count, quantized_cg);
// Apply dequantization (perceptual for version 5, uniform for earlier versions)
const int is_perceptual = (decoder->header.version == 5);

89
video_encoder/encoder_tav.c
View File

@@ -74,6 +74,9 @@ int KEYFRAME_INTERVAL = 2; // refresh often because deltas in DWT are more visib
#define MP2_DEFAULT_PACKET_SIZE 1152
#define MAX_SUBTITLE_LENGTH 2048
const int makeDebugDump = -100; // enter a frame number
int debugDumpMade = 0;
// Subtitle structure
typedef struct subtitle_entry {
int start_frame;
@@ -954,6 +957,38 @@ static void dwt_2d_forward_flexible(float *tile_data, int width, int height, int
free(temp_col);
}
// Preprocess coefficients using significance map for better compression
static size_t preprocess_coefficients(int16_t *coeffs, int coeff_count, uint8_t *output_buffer) {
// Count non-zero coefficients
int nonzero_count = 0;
for (int i = 0; i < coeff_count; i++) {
if (coeffs[i] != 0) nonzero_count++;
}
// Create significance map (1 bit per coefficient, packed into bytes)
int map_bytes = (coeff_count + 7) / 8; // Round up to nearest byte
uint8_t *sig_map = output_buffer;
int16_t *values = (int16_t *)(output_buffer + map_bytes);
// Clear significance map
memset(sig_map, 0, map_bytes);
// Fill significance map and extract non-zero values
int value_idx = 0;
for (int i = 0; i < coeff_count; i++) {
if (coeffs[i] != 0) {
// Set bit in significance map
int byte_idx = i / 8;
int bit_idx = i % 8;
sig_map[byte_idx] |= (1 << bit_idx);
// Store the value
values[value_idx++] = coeffs[i];
}
}
return map_bytes + (nonzero_count * sizeof(int16_t));
}
// Quantisation for DWT subbands with rate control
static void quantise_dwt_coefficients(float *coeffs, int16_t *quantised, int size, int quantiser) {
@@ -1276,10 +1311,56 @@ static size_t serialise_tile_data(tav_encoder_t *enc, int tile_x, int tile_y,
printf("\n");
}*/
// Write quantised coefficients (both uniform and perceptual use same linear layout)
memcpy(buffer + offset, quantised_y, tile_size * sizeof(int16_t)); offset += tile_size * sizeof(int16_t);
memcpy(buffer + offset, quantised_co, tile_size * sizeof(int16_t)); offset += tile_size * sizeof(int16_t);
memcpy(buffer + offset, quantised_cg, tile_size * sizeof(int16_t)); offset += tile_size * sizeof(int16_t);
// Preprocess and write quantised coefficients using significance mapping for better compression
size_t y_compressed_size = preprocess_coefficients(quantised_y, tile_size, buffer + offset);
offset += y_compressed_size;
size_t co_compressed_size = preprocess_coefficients(quantised_co, tile_size, buffer + offset);
offset += co_compressed_size;
size_t cg_compressed_size = preprocess_coefficients(quantised_cg, tile_size, buffer + offset);
offset += cg_compressed_size;
// DEBUG: Dump raw DWT coefficients for frame ~60 when it's an intra-frame
if (!debugDumpMade && enc->frame_count >= makeDebugDump - 1 && enc->frame_count <= makeDebugDump + 2 &&
(mode == TAV_MODE_INTRA)) {
char filename[256];
size_t data_size = tile_size * sizeof(int16_t);
// Dump Y channel coefficients
snprintf(filename, sizeof(filename), "frame_%03d.tavframe.y.bin", enc->frame_count);
FILE *debug_fp = fopen(filename, "wb");
if (debug_fp) {
fwrite(quantised_y, 1, data_size, debug_fp);
fclose(debug_fp);
printf("DEBUG: Dumped Y coefficients to %s (%zu bytes)\n", filename, data_size);
}
// Dump Co channel coefficients
snprintf(filename, sizeof(filename), "frame_%03d.tavframe.co.bin", enc->frame_count);
debug_fp = fopen(filename, "wb");
if (debug_fp) {
fwrite(quantised_co, 1, data_size, debug_fp);
fclose(debug_fp);
printf("DEBUG: Dumped Co coefficients to %s (%zu bytes)\n", filename, data_size);
}
// Dump Cg channel coefficients
snprintf(filename, sizeof(filename), "frame_%03d.tavframe.cg.bin", enc->frame_count);
debug_fp = fopen(filename, "wb");
if (debug_fp) {
fwrite(quantised_cg, 1, data_size, debug_fp);
fclose(debug_fp);
printf("DEBUG: Dumped Cg coefficients to %s (%zu bytes)\n", filename, data_size);
}
printf("DEBUG: Frame %d - Dumped all %zu coefficient bytes per channel (total: %zu bytes)\n",
enc->frame_count, data_size, data_size * 3);
debugDumpMade = 1;
}
// OPTIMISATION: No need to free - using pre-allocated reusable buffers